1. Technical Field
The present invention relates to a disc gripping device suitable to be used for gripping discs one by one which are loaded in a stacker of a device such as a disc dubbing device and a CD/DVD publisher.
2. Related Art
In a disc processing device such as a disc dubbing device, which writes data in multiple discs such as blank CDs, and a CD/DVD publisher, which can publish a disc using a produced disc by writing data and printing a label, generally, multiple blank discs or recorded discs are loaded into a stacker so that the discs are stacked in a thickness direction. Gripping devices for gripping a disc loaded in a stacker are known in JP-A-2003-257084 (Patent Document 1) and U.S. Pat. No. 6,802,070 (Patent Document 2).
In Patent Document 1, an optical disc clamping device is disclosed. In the optical disc clamping device, steel balls separated by equal angular distances in the same circle are pushed outward in a radial direction by an elastic force. The steel balls are inserted into a center hole from a front side of the disc to be pushed out to a rear side of the disc. When the steel balls are pushed to the rear side of the disc off the inner circumference face of the center hole, the steel balls are expanded outward in the radial direction depending on an elastic force, and the disc is gripped by the steel balls.
In Patent Document 2, a CD transporting device is disclosed. In this CD transporting device, a CD separation protrusion is formed on a gripping part of a gripping member for assuredly gripping one CD that is disposed in the uppermost position among CDs stacked in a thickness direction. In this CD transporting device, only the uppermost CD is gripped and lifted by pushing the three gripping parts inserted into the center hole of the CD and inserting the protrusions thereof into a gap between the CD and a CD stacked in the lower side.
In the optical disc clamping device disclosed in Patent Document 1, the steel balls pushed by an elastic force are forcedly inserted into the center hole of the disc to be lifted to the rear side of the disc. Accordingly, there is a possibility that an inner circumference face part or an edged end part of the center hole of the disc is damaged by the steel balls. In addition, in a case where discs are stacked up, when the steel balls are moved to a rear side of the uppermost disc, the steel balls contact the inner circumference face of the center hole of a lower disc. Thus, the steel balls cannot move inward in the radial direction when the upper and lower discs are tightly contacted to each other by an electrostatic force or the like, and there is a possibility that only the upper disc cannot be gripped.
In the CD transporting device disclosed in Patent Document 2, upper and lower discs are separated by the protrusion formed on the gripping part, and accordingly, only the upper disc can be gripped and lifted. However, the depth of a disc such as a CD differs by a disc manufacturer. In addition, there is a thickness difference between different types of discs such as between a CD and a DVD. Accordingly, a situation may arise where the position of the protrusion of the gripping part cannot be determined between the upper and lower discs, and only the upper disc cannot be gripped and lifted.